Bacterial Viruses in the Sea 361 



the effect of sea water in minimizing thermal inactivation is 

 probably a "balanced salt" effect. 



Effect of Incubation Temperature on the Ability to 

 Lyse the Host Organism 



The bacteria against which the phages were isolated were all 

 psychrophilic, that is, were capable of growing at temperatures 

 around 0° C and consequently the ability of the phages to cause 

 lysis at such a low temperature was investigated. Sea water 

 Lemco agar plates, surface seeded with the appropriate bacterial 

 strain, together with samples of the phage preparations, were 

 placed in a refrigerator fitted with a recording thermometer and 

 running at 1 C ± 1 C. After some hours had elapsed and the 

 inoculated plates and phage preparations had reached the am- 

 bient temperature of the refrigerator, drops of the phage pre- 

 paration were placed on the surface of the cultures. The plates 

 were then left in the refrigerator for up to twenty-one days for 

 bacterial growth to occur. In all cases, lysis developed. All the 

 phages would thus appear to be capable of multiplication at 

 the low temperatures of their environment. The only other re- 

 port of a phage able to multiply at such low temperatures would 

 appear to be that of Elder and Tanner (7). 



Several of the phages were unable to cause lysis, under the 

 experimental conditions used, at temperatures such as 30 or 

 37 C at which the host bacterial strain grew well. The phe- 

 nomenon was most marked, however, witli P/14 which would 

 not cause lysis at 22 C, although it would at 21 C. The host strain 

 would grow at temperatures up to 25 to 28 C. 



THE EFFECT OF SALINITY 



Survival in Sea Water 



Because of the sparse bacterial population of the open seas, 

 it is probable that marine phages would need to be capable of 

 prolonged survi\al in sea water at temperatures between and 20 

 C to ensure eventual contact with a sensitive bacterial cell. This 

 ability was investigated by adding phage preparations to 2.5 

 liter amounts of sea water, previously membrane filtered to re- 

 move bacteria which would interfere with the subsequent phage 



